Electrically insulated cable

ABSTRACT

An electrically insulated cable comprising: a core electric wire; a tape member covering the core electric wire; and a covering layer covering the tape member; wherein: the core electric wire includes a plurality of insulated electric wires; the insulated electric wires each include a conductor and an insulating layer covering the conductor; and the tape member has a minimum value of transmittance of 70% or more with respect to light having a wavelength of no less than 400 nm and no more than 800 nm.

TECHNICAL FIELD

The present disclosure relates to an electrically insulated cable. Thepresent application claims priority of Japanese Patent Application No.2019-197607 filed on Oct. 30, 2019, the contents of which are herebyincorporated by reference in its entirety.

BACKGROUND ART

Electric parking brake (EPB) systems to be mounted on vehicles each usean electrically insulated cable (a cable for EPB) that electricallyconnects a caliper in a wheel house and an electronic control unit onthe body side of a vehicle.

CITATION LIST Patent Literature

-   PTL 1: Japanese Patent Laying-Open No. 2015-156386-   PTL 2: Japanese Patent Laying-Open No. 2017-162644

SUMMARY OF INVENTION

The electrically insulated cable according to the present disclosure isan electrically insulated cable comprising:

a core electric wire;

a tape member covering the core electric wire; and

a covering layer covering the tape member;

wherein:

the core electric wire includes a plurality of insulated electric wires;

the insulated electric wires each include a conductor and an insulatinglayer covering the conductor; and

the tape member has a minimum value of transmittance of 70% or more withrespect to light having a wavelength in the range of no less than 400 nmand no more than 800 nm.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view showing a configuration of anembodiment of the electrically insulated cable of the presentdisclosure.

FIG. 2 is a cross-sectional view showing a configuration of anotherembodiment of the electrically insulated cable of the presentdisclosure.

FIG. 3 is a cross-sectional view showing a configuration of furtheranother embodiment of the electrically insulated cable of the presentdisclosure.

FIG. 4 is a schematic configuration diagram showing a manufacturingapparatus for manufacturing an electrically insulated cable according toone aspect of the present embodiment.

DETAILED DESCRIPTION Problem to be Solved by the Present Disclosure

Japanese Patent Laying-Open No. 2015-156386 (PTL 1) discloses anelectrically insulated cable comprising: a core electric wire formed bytwisting a plurality of core materials including a conductor and aninsulating layer formed so as to cover the conductor; a first coveringlayer formed so as to cover the core electric wire; a second coveringlayer formed so as to cover the first covering layer; and a tape memberarranged, between the core electric wire and the first covering layer,in a state of winding around the core electric wire; wherein: the secondcovering layer is formed of a flame-retardant polyurethane-based resin,and the cross-sectional area of each of the conductors is in the rangeof 0.18 to 3.0 mm².

Japanese Patent Laying-Open No. 2017-162644 (PTL 2) discloses acomposite cable comprising: a first pair twisted wire formed by twistinga pair of first electric wires each having a first central conductor anda first insulator covering the first central conductor on the outercircumference thereof; a second pair twisted wire formed by twisting apair of second electric wires each having a second central conductor anda second insulator covering the second central conductor on the outercircumference thereof; a pair of third electric wires that each have athird central conductor having a cross-sectional area larger than thefirst central conductor and the second central conductor and a thirdinsulator covering the third central conductor on the outercircumference thereof, that each have an outer diameter larger than thefirst electric wire and the second electric wire, and that each arearranged between the first pair twisted wire and the second pair twistedwire in the outer circumference direction; and a tape member woundspirally around an assembly formed by twisting together the first pairtwisted wire, the second twisted wire and the pair of the third electricwire; wherein: the twisting directions of both the pair twisted wiresare the same as each other, the twisting directions of both the pairtwisted wires are different from the twisting direction of the assembly,and the twisting direction of the assembly is different from the windingdirection of the tape member.

The tape member of each of PTL 1 and PTL 2 is formed of paper, anonwoven fabric or the like. Therefore, when the tape member covers thecore electric wire in the manufacturing process, the state of the corematerial (insulated electric wire) constituting the core electric wire(such as the presence or absence of a bump in the insulating layer, thepresence or absence of a contaminant or disordered twisting of theassembly) cannot be confirmed in the subsequent process. Accordingly,further improvement has been required from the viewpoint of improvingthe yield.

The present disclosure has been made in view of the above circumstances,and an object of the present invention is to provide an electricallyinsulated cable excellent in visibility, even if a core electric wire iscovered with a tape member, for an insulated electric wire includedtherein.

Advantageous Effect of the Present Disclosure

According to the present disclosure, it is possible to provide anelectrically insulated cable excellent in visibility, even if a coreelectric wire is covered with a tape member, for an insulated electricwire included therein.

DESCRIPTION OF EMBODIMENTS

First, implementations of the present disclosure will be listed anddescribed.

[1] The electrically insulated cable according to one aspect of thepresent disclosure is an electrically insulated cable comprising:

a core electric wire;

a tape member covering the core electric wire; and

a covering layer covering the tape member;

wherein:

the core electric wire includes a plurality of insulated electric wires;

the insulated electric wires each include a conductor and an insulatinglayer covering the conductor; and

the tape member has a minimum value of transmittance of 70% or more withrespect to light having a wavelength in the range of no less than 400 nmand no more than 800 nm.

In the electrically insulated cable according to the present disclosure,the tape member covering the core electric wire is transparent in apredetermined wavelength region. Therefore, it is possible to provide anelectrically insulated cable excellent in visibility, even if a coreelectric wire is covered with a tape member, for an insulated electricwire included therein. As used herein, the term “visibility” is notlimited to the property of being able to confirm an object by the nakedeye, but also includes the property of being able to detect the objectwith a camera.

[2] The tape member preferably comprises at least one compound selectedfrom the group consisting of cellulose, polyethylene terephthalate andpolyethylene. By defining in this way, the electrically insulated cablebecomes further excellent in the above-described visibility.

[3] The thickness of the tape member is preferably no less than 3 μm andno more than 200 μm. By defining in this way, the electrically insulatedcable becomes excellent in the stability to the outer diameter of thecore electric wire in addition to the above-described visibility.

[4] The covering layer preferably includes a first sheath layer coveringthe tape member and a second sheath layer covering the first sheathlayer. By defining in this way, the electrically insulated cable canhave an excellent impact resistance in addition to the above-describedvisibility. As used herein, the term “impact resistance” means aresistance to damage to an electrically insulated cable due to anexternal impact.

[5] The plurality of insulated electric wires each have the samediameter, and the conductor in each of the plurality of insulatedelectric wires preferably has a cross-sectional area of no less than 1.5mm² and no more than 3 mm². By defining in this way, the electricallyinsulated cable can have excellent electrical characteristics and anexcellent flexing resistance.

[6] The electrically insulated cable is preferably an electricallyinsulated cable to be mounted on a vehicle. The electrically insulatedcable can be suitably used to be mounted on a vehicle.

[7] The electrically insulated cable is preferably an electricallyinsulated cable for an electric parking brake. The electricallyinsulated cable can be suitably used for an electric parking brake.

[8] The electrically insulated cable is preferably an electricallyinsulated cable for an antilock brake system. The electrically insulatedcable can be suitably used for an antilock brake system.

Details of Embodiments

Hereinafter, embodiments of the present disclosure (hereinafter referredto as “the present embodiment”) will be described. However, the presentembodiments are not limited thereto. As used herein, the expression inthe form of “A to Z” means the upper limit and the lower limit of arange (that is, no less than A and no more than Z), and when there is nodescription of the unit for A and the unit is described only for Z, theunit for A is the same as the unit of Z.

<<Electrically Insulated Cable>>

The electrically insulated cable according to the present disclosure(hereinafter sometimes referred to only as “electrically insulatedcable”) is an electrically insulated cable comprising:

a core electric wire;

a tape member covering the core electric wire; and

a covering layer covering the tape member;

wherein:

the core electric wire includes a plurality of insulated electric wires;

the insulated electric wires each include a conductor and an insulatinglayer covering the conductor; and

the tape member has a minimum value of transmittance of 70% or more withrespect to light having a wavelength in the range of no less than 400 nmand no more than 800 nm.

FIG. 1 is a cross-sectional view showing a configuration of anembodiment of the electrically insulated cable of the presentdisclosure. An electrically insulated cable 50 shown in FIG. 1 is used,for example, for an electric parking brake. Electrically insulated cable50 comprises a core electric wire 14, a tape member 15 covering coreelectric wire 14, and a covering layer 18 covering tape member 15. InFIG. 1 , core electric wire 14 includes two insulated electric wires 13.Two insulated electric wires 13 are bundled by winding tape member 15around insulated electric wires 13 on the outer circumference thereof.Insulated electric wire 13 includes a conductor 11 and an insulatinglayer 12 covering conductor 11. Covering layer 18 includes a firstsheath layer 16 covering tape member 15 and a second sheath layer 17covering first sheath layer 16. Hereinafter, each of the componentsconstituting the electrically insulated cable will be described.

<Core Electric Wire>

The core electric wire includes a plurality of insulated electric wires(also referred to as “insulated wires”). In other words, it can also beunderstood that an assembly of a plurality of insulated electric wiresis a core electric wire. The core electric wire may be, for example, atwisted wire formed by twisting a plurality of the insulated electricwires.

The number of the insulated electric wires constituting the coreelectric wire is not particularly limited, but may be, for example, two,four or six. The diameters (outer diameters) of the plurality ofinsulated electric wires constituting the core electric wire may be eachthe same as or different from each other. For example, two or moreinsulated electric wires each having substantially the same diameter maybe twisted together to form a core electric wire (for example, FIG. 1 ).A plurality of insulated electric wires having different diameters maybe twisted together to form a core electric wire (for example, FIG. 2 ).

The core electric wire can include insulated electric wires for two ormore applications. For example, insulated electric wires (two or more)for EPB having substantially the same diameter can be twisted togetherwith an insulated electric wire(s) for a signal or grounding having adiameter smaller than the diameter of the insulated electric wire forEPB to form a single core electric wire.

(Insulated Electric Wire)

The insulated electric wire includes a conductor and an insulating layercovering the conductor. The term “conductor” as used in the presentembodiment means a wire material comprised of a material havingelectrical conductivity, ductility and malleability. The materialconstituting the conductor is not particularly limited, but examplesthereof include copper, aluminum, a copper alloy, tin-plated copper andan aluminum alloy. The conductor may be a single element wire or atwisted wire formed by twisting a plurality of (tens to hundreds of)element wires together. The conductor may be also a twisted wire formedby further twisting such twisted wires together.

When the electrically insulated cable is used for power supplyapplications (for example, when used as a cable for EPB), thecross-sectional area of the conductor (in the case of being composed ofa plurality of element wires, the total cross-sectional area thereof) ispreferably no less than 1.5 mm² and no more than 3 mm², and morepreferably no less than 1.6 mm² and no more than 2.5 mm².

When the electrically insulated cable is used for signal lineapplications (for example, when used as a cable for ABS), thecross-sectional area of the conductor is preferably no less than 0.13mm² and no more than 0.5 mm², and more preferably no less than 0.18 mm²and no more than 0.35 mm². The cross-sectional area of the conductor canbe determined by the following procedure. First, the diameter of each ofthe element wires (approximately 5 element wires) is measured using amicrometer gauge or the like, and the “average diameter of elementwires” is calculated by averaging the diameters measured from each ofthe element wires. Next, the cross-sectional area per element wire iscalculated from the calculated average diameter of element wires. Atthis time, the cross section perpendicular to the longitudinal directionof the element wire is assumed to be a circle to calculate thecross-sectional area thereof. The cross-sectional area of the conductoris determined by multiplying the calculated cross-sectional area by thenumber of element wires constituting the conductor.

In one aspect of the present embodiment, the plurality of insulatedelectric wires each have the same diameter, and the conductor in each ofthe plurality of insulated electric wires preferably has across-sectional area of no less than 1.5 mm² and no more than 3 mm². Asused herein, the term “the same” is intended to include not only“completely the same” but also “substantially the same”.

Examples of the material constituting the insulating layer include apolyolefin-based resin. The polyolefin-based resin is preferably aflame-retardant polyolefin-based resin. The flame-retardantpolyolefin-based resin can be produced, for example, by blending aconventional polyolefin-based resin with a flame retardant. Due to theinsulating layer being composed of the flame-retardant polyolefin-basedresin, the flame retardant properties and the insulating properties ofthe core electric wire (insulated electric wire) can be ensured, evenwhen a part of the core electric wire (insulated electric wire) isexposed by removing the covering layer or the tape member.

Examples of the polyolefin-based resin include, but not limited to, ahigh-density polyethylene (HDPE), a low-density polyethylene (LDPE), alinear low-density polyethylene (LLDPE), a very low-density polyethylene(VLDPE), an ethylene-vinyl acetate copolymer resin (EVA), anethylene-methyl acrylate copolymer resin (EMA) and an ethylene-ethylacrylate copolymer resin (EEA). Examples of the material constitutingthe insulating layer also include other materials such as afluorine-based resin.

In the case of an insulated electric wire used for a cable for EPB, thethickness of the insulating layer is preferably no less than 0.2 mm andno more than 0.8 mm, and more preferably no less than 0.25 mm and nomore than 0.7 mm. As used herein, the “thickness of the insulatinglayer” means the shortest distance from the inner wall of the insulatinglayer to the outer wall of the insulating layer. The thickness of theinsulating layer can be determined as follows. First, for arbitrarilyselected 10 points in the insulating layer, the thickness of theinsulating layer at each of the selected 10 points is measured using aslide caliper or a micrometer gauge. Next, the value calculated byaveraging the thicknesses measured at each point is taken as thethickness of the insulating layer.

The outer diameter of the insulated electric wire is preferably no lessthan 2.5 mm and no more than 4 mm, and more preferably no less than 2.5mm and no more than 3.8 mm. The outer diameter of the insulated electricwire can be measured, for example, with a slide caliper.

<Tape Member>

The tape member covers the core electric wire. In one aspect of thepresent embodiment, it can also be understood that the tape member isarranged between the core electric wire and the covering layer describedlater. It can also be understood that the tape member winds around theouter circumference of the core electric wire (the outer circumferenceof the assembly of insulated electric wires).

The tape member has a minimum value of transmittance of 70% or more in awavelength range of no less than 400 nm and no more than 800 nm. In oneaspect of the present embodiment, the tape member can be understood tohave a minimum value of transmittance of 70% or more with respect tolight having a wavelength in the range of no less than 400 nm and nomore than 800 nm. By defining in this way, the tape member transmitlight in a predetermined wavelength region. As a result, even if thecore electric wire is covered with the tape member, the state of theinsulated electric wire (core electric wire) included therein can bevisually recognized.

The minimum value of the transmittance of the tape member in theabove-described wavelength region is preferably no less than 70% and nomore than 100%, and more preferably no less than 80% and no more than100%. The transmittance can be calculated by measuring the transmissionspectrum in the predetermined wavelength range described above. Forexample, a device for measuring the transmission spectrum to be used isUV-2450 (trade name) manufactured by Shimadzu Corporation.

The tape member is desired to have such strength that can preventfailure due to repeated flexing. The tape member usually winds aroundthe outer circumference of the core electric wire, and in this case,ease of winding is desired. The thickness and shape (such as width) ofthe tape member and the material for forming the tape member arepreferably selected in consideration of its strength and ease ofwinding.

From the above viewpoint, examples of the material constituting the tapemember include cellulose, polyethylene terephthalate and polyethylene.That is, the tape member preferably comprises at least one compoundselected from the group consisting of cellulose, polyethyleneterephthalate and polyethylene. Among them, the tape member morepreferably comprises polyethylene terephthalate. Examples of the tapemember comprised of the cellulose include cellophane.

In one aspect of the present embodiment, the tape member has a minimumvalue of transmittance of 70% or more with respect to light having awavelength in the range of no less than 400 nm and no more than 800 nm,and the tape member preferably comprises at least one compound selectedfrom the group consisting of cellulose, polyethylene terephthalate andpolyethylene.

Heretofore, it has been common to use paper, a nonwoven fabric or thelike as a tape member. When an electrically insulated cable is exposedto severe vibration conditions, the electrically insulated cable isrequired to have an excellent flexing resistance. However, when paper ora nonwoven fabric is used as the tape member, the tape member tends tobe easily failed by repeatedly flexing the electrically insulatingcable. The electrically insulated cable according to the presentembodiment combines an excellent visibility and such strength that canprevent failure due to repeated flexing, by using the tape member havingthe above-described configuration. The electrically insulated cablecomprising the tape member as described above is preferably used as anelectrical insulating cable to be mounted on a vehicle that will beexposed to severe vibration conditions, particularly an electricallyinsulated cable for an electric parking brake or an electricallyinsulated cable for an antilock braking system.

The thickness of the tape member is preferably no less than 3 μm and nomore than 200 μm. When the thickness is thinner than 3 μm, the tapemember tends to be easily stretched when wound around the core electricwire on the outer circumference thereof. When the thickness is thickerthan 200 μm, the rigidity of the tape member is high and the tape tendsto easily spread even when wound, and the outer diameter of the coveringlayer that is covered after winding tends to become unstable. Thethickness of the tape member can be measured, for example, by amicrometer gauge with a columnar spindle having a flat tip and adiameter of 10 mm. At this time, the thickness is first measured at eachof arbitrarily selected 10 points of the tape member, and the averagevalue of the thicknesses measured at the selected 10 points is taken asthe thickness of the tape member.

In addition, when the core electric wire is covered with the tape memberand the covering layer is thereafter formed on the tape member on theouter circumference thereof, for example, by melt extrusion of a resinwhich is a material for the covering layer, the tape member is desirednot to be softened by the heating during the melt extrusion. Therefore,the tape member is preferably composed of a material having a meltingpoint higher than that of the material constituting the covering layer.Specifically, the tape member is preferably composed of a materialhaving a melting point of 160° C. or more, such as polyethyleneterephthalate. When the melting point is less than 160° C., the tapemember may be melted or deformed in the process of forming the coveringlayer on the outer circumference of the tape member.

<Covering Layer>

The covering layer of the present disclosure covers the tape member. Inone aspect of the present embodiment, the covering layer can also beunderstood to cover the outer circumference of the core electric wirebundled by the tape member. The covering layer protects the coreelectric wire. That is, the covering layer is required to be flexible toensure resistance to stone splash or the like during driving a motorvehicle (impact resistance) and flexibility of the electricallyinsulated cable. The covering layer is also required to have anexcellent flexing resistance or the like so as not to causedeterioration, such as disconnection and increase in resistance, of theconductor due to repeated flexing during traveling. In one aspect of thepresent embodiment, the covering layer may or may not be transparent tovisible light.

The covering layer may be composed of a single layer (see, for example,FIG. 3 ). In this case, any of a material constituting the first sheathlayer described later and a material constituting the second sheathlayer described later can be used as the material constituting thecovering layer.

The covering layer may be composed of two or more layers. That is, thecovering layer preferably includes a first sheath layer covering thetape member and a second sheath layer covering the first sheath layer.For example, an electrically insulated cable to be mounted on a vehiclesuch as a cable for EPB or a cable for ABS can have a two-layerstructure in which a covering layer is comprised of a first sheath layercovering a tape member (core electric wire) and a second sheath layercovering the first sheath layer (see FIGS. 1 and 2 ).

(First Sheath Layer)

In order to improve the flexibility of the electrically insulated cable,the material constituting the first sheath layer is preferably amaterial excellent in flexibility. Particularly, when the elasticmodulus of the first sheath layer in a low temperature environment islarge, the flexing resistance of the electrically insulated cable in alow temperature environment tends to decrease. Therefore, in order toimprove the flexing resistance of the electrically insulated cable in alow temperature environment, the material for the first sheath layer tobe used is preferably a material flexible in a low temperatureenvironment. In the case of the electrically insulated cable to bemounted on a vehicle, the material for the first sheath layer is furtherdesired to be excellent in wear resistance, heat resistance or the likeand it is often also desired to have flame retardance.

Examples of the material constituting the first sheath layer include apolyolefin-based resin such as polyethylene and an ethylene-vinylacetate copolymer resin (EVA), a polyurethane elastomer, a polyesterelastomer and a resin obtained by mixing these. By forming the firstsheath layer out of a polyolefin-based resin, the electrically insulatedcable can be improved in flexibility and flexing resistance in a lowtemperature environment. By forming the first sheath layer out of apolyurethane elastomer, the electrically insulated cable can be improvedin wear resistance. By forming the first sheath layer out of a polyesterelastomer, the electrically insulted cable can be also improved in heatresistance. Among the above-described resins, the polyethylene-basedresin is particularly preferred from the viewpoint of a manufacturingcost and the like.

The material constituting the first sheath layer to be used can be aresin containing very low-density polyethylene (VLDPE) as a maincomponent and having a small ratio between the elastic modulus in a lowtemperature environment and the elastic modulus in a high temperatureenvironment. By using such a resin, it is possible to manufacture anelectrically insulated cable having an excellent flexing resistance in awide temperature range from room temperature to a low temperature. Theresin containing VLDPE as a main component may be blended with otherresins such as EVA, an ethylene-ethyl acrylate copolymer resin (EEA) andan acid-modified VLDPE, as long as the effects of the present disclosureare exhibited.

The material for forming the first sheath layer may contain variousadditives such as an antioxidant, a colorant and a flame retardant, aslong as the effects of the present disclosure are exhibited.

When the electrically insulated cable is a power wire (such as a cablefor EPB) used for power supply applications, the thickness of the firstsheath layer is usually preferably no less than 0.3 mm and no more than1.5 mm and more preferably no less than 0.45 mm and no more than 1.2 mm.As used herein, the “thickness of the first sheath layer” means theshortest distance from the inner wall of the first sheath layer to theouter wall of the first sheath layer. The thickness of the first sheathlayer can be measured using a slide caliper or a micrometer gauge in thesame manner as described above (average value of 10-point measurements).

(Second Sheath Layer)

The second sheath layer covers the above-described first sheath layer.In one aspect of the present embodiment, the second sheath layer canalso be understood to be the outermost sheath layer of the electricallyinsulated cable. In the case of an electrically insulated cable (such asa cable for EPB) to be mounted on a vehicle, it is subject to damage bystone splash or the like during traveling. In order to prevent thedamage, the material constituting the second sheath layer is desired tobe a resin excellent in flaw resistance and wear resistance. Inaddition, in order to make the electrically insulated cable flexible,the material constituting the second sheath layer is desired to be amaterial excellent in flexibility. Furthermore, when the electricallyinsulated cable is desired to have flame retardance, the second sheathlayer is desired to have a high flame retardance.

Therefore, the material constituting the second sheath layer to be usedis preferably a polyurethane-based resin such as a flame-retardantpolyurethane resin, from the viewpoint of flaw resistance, flexibilityand the like.

When the electrically insulated cable is a power wire (such as a cablefor EPB) used for power supply applications, the thickness of the secondsheath layer is usually preferably no less than 0.3 mm and no more than0.7 mm. As used herein, the “thickness of the second sheath layer” meansthe shortest distance from the inner wall of the second sheath layer tothe outer wall of the second sheath layer. The thickness of the secondsheath layer can be measured using a slide caliper or a micrometer gaugein the same manner as described above (average value of 10-pointmeasurements).

Embodiments of Electrically Insulated Cable of the Present Disclosure

Hereinafter, more specific embodiments of the above-describedelectrically insulated cable will be described.

Embodiment 1

FIG. 1 is a cross-sectional view showing Embodiment 1 of theelectrically insulated cable of the present disclosure. An electricallyinsulated cable 50 shown in FIG. 1 is an electrically insulated cableused as a cable for EPB. Electrically insulated cable 50 has a coreelectric wire 14 formed by twisting together two twisted insulatedelectric wires 13. A covering layer 18 covering core electric wire 14 iscomprised of a first sheath layer 16 and a second sheath layer 17.

In FIG. 1 , insulated electric wires 13 are each comprised of aconductor 11 and an insulating layer 12 covering conductor 11. Conductor11 is a twisted wire (a total of 504 element wires) formed by formingtwisted wires using 72 element wires, made from a copper alloy, havingan outer diameter of 0.08 mm and further twisting the seven twistedwires. The outer diameter of conductor 11 is approximately 2.4 mm.Insulating layer 12 comprised of a flame-retardant polyethylene coversconductor 11 on the outer circumference thereof. The thickness ofinsulating layer 12 is approximately 0.5 mm. Core electric wire 14 isformed by twisting together the two insulated electric wires 13 thusformed.

A tape member 15 is spirally wound around core electric wire 14 on theouter circumference thereof to cover the entire outer circumference ofcore electric wire 14. Tape member 15 has a minimum value oftransmittance of 70% or more with respect to light having a wavelengthin the range of no less than 400 nm and no more than 800 nm. Tape member15 is a transparent tape having a width of approximately 5 mm and athickness of approximately 0.033 mm. Polyethylene terephthalate is usedas tape member 15. Tape member 15 has such flexibility that enables easywinding, and such strength that is not easily failed by flexing anelectrically insulating cable or the like. In addition, a material to beused for tape member 15 is preferably a material that is not softened byheat during formation of covering layer 18 (during melt extrusion of aresin).

First sheath layer 16 is comprised of polyethylene. The thickness offirst sheath layer 16 is approximately 0.6 mm. Second sheath layer 17 iscomprised of polyurethane. The thickness of second sheath layer 17 isapproximately 0.5 mm. The material constituting first sheath layer 16 isnot limited to polyethylene, but the material to be used is preferably aresin that improves flame retardance, wear resistance and flexingresistance (flexibility) of the electrically insulated cable. Thematerial constituting second sheath layer 17 is not limited topolyurethane, but the material to be used is preferably a resinexcellent in flame retardance, flaw resistance and flexing resistance(flexibility). The outer diameter of electrically insulated cable 50 isapproximately 8 mm to 9 mm.

Embodiment 2

FIG. 2 is a cross-sectional view showing another example of theembodiment of the electrically insulated cable of the presentdisclosure. An electrically insulated cable 60 shown in FIG. 2 is anelectrically insulated cable used as a cable for EPB and ABS.Electrically insulated cable 60 has a core electric wire 24 formed bytwisting together four insulated electric wires (two insulated electricwires 23 a and two insulated electric wires 23 b). A covering layer 28covering core electric wire 24 is comprised of a first sheath layer 26and a second sheath layer 27.

In FIG. 2 , insulated electric wires 23 a are each comprised of aconductor 21 a and an insulating layer 22 a covering conductor 21 a.Conductor 21 a is a twisted twisted wire (a total of 504 element wires)formed by forming twisted wires using 72 element wires, made from acopper alloy, having an outer diameter of 0.08 mm and further twistingthe seven twisted wires. The outer diameter of conductor 21 a isapproximately 2.4 mm. Insulating layer 22 a comprised of aflame-retardant polyethylene and having a thickness of approximately 0.5mm covers conductor 21 a on the outer circumference thereof. Insulatedelectric wire 23 a transmits electric power for EPB. On the other hand,insulated electric wires 23 b are each comprised of a conductor 21 b andan insulating layer 22 b covering conductor 21 b. Conductor 21 b is atwisted wire formed by twisting together 48 element wires, made of acopper alloy, having an outer diameter of approximately 0.08 mm. Theouter diameter of conductor 21 b is approximately 0.7 mm. Insulatinglayer 22 b comprised of a flame-retardant polyethylene and having athickness of approximately 0.4 mm covers conductor 21 b on the outercircumference thereof. Insulated electric wire 23 b transmits electricpower for ABS. Core electric wire 24 is formed by twisting together thetwo insulated electric wires 23 a and the two insulated electric wires23 b thus formed.

A tape member 25 is spirally wound around core electric wire 24 on theouter circumference thereof to cover the entire outer circumference ofcore electric wire 24. Tape member 25 has a minimum value oftransmittance of 70% or more with respect to light having a wavelengthin the range of no less than 400 nm and no more than 800 nm. Tape member25 to be used can be a tape having the same width and thickness as thoseof Example 1 of the embodiment. The same material as the material forforming tape member 15 can be used as a material for forming tape member25.

The thickness of first sheath layer 26 can be as the same thickness asthat of first sheath layer 16 of Example 1 of the embodiment. Inaddition, the same material as the material for forming first sheathlayer 16 can be used as a material for forming first sheath layer 26.The thickness of second sheath layer 27 can be as the same thickness asthat of second sheath layer 17 of Example 1 of the embodiment. Inaddition, the same material as the material for forming second sheathlayer 17 can be used as a material for forming second sheath layer 27.The outer diameter of electrically insulated cable 60 is approximately 8mm to 9 mm.

Hereinbefore, the electrically insulated cable according to the presentembodiment has been described in detail. The above-describedelectrically insulated cable is used as a member for making anelectrical connection in various devices. The above-describedelectrically insulated cable is suitably used as an electricallyinsulated cable to be mounted on a vehicle, particularly as a cable thatis used in such applications as an electric parking brake (EPB) systemand an antilock brake system (ABS). That is, the above-describedelectrically insulated cable is preferably an electrically insulatedcable for an electric parking brake. In addition, the above-describedelectrically insulated cable is preferably an electrically insulatedcable for an antilock brake system.

In addition, by forming the covering layer out of a transparent resin,the electrically insulated cable also becomes suitable as a model cablefor characteristic evaluation used in the development stage. By usingthe electrically insulated cable according to the present disclosure asa model cable, it becomes easy to observe the behavior and state of theinside of the cable when flexed or extended.

<<Manufacturing Method of Electrically Insulated Cable>>

Next, a method for manufacturing an electrically insulated cable of thepresent disclosure will be described. FIG. 4 is a schematicconfiguration diagram showing a manufacturing apparatus formanufacturing an electrically insulated cable according to one aspect ofthe present embodiment. As shown in FIG. 4 , a manufacturing apparatus111 comprises two insulated electric wire supply reels 112, a twistingsection 113, a tape member supply reel 114, a tape member-windingsection 115, a first sheath layer-covering section 116, a second sheathlayer-covering section 117, a cooling section 118, and an electricallyinsulated cable winding reel 119.

An insulated electric wire 13 is wound around each of two insulatedelectric wire supply reels 112, and two insulated electric wires 13 aresupplied to twisting section 113. Here, insulated electric wire 13 canbe manufactured by covering conductor 11 as described above on the outercircumference thereof with an insulating resin which is a materialconstituting an insulating layer 12 (hereinafter sometimes referred toas “insulating resin”). Covering with the insulating resin can becarried out by the same method as in the case of manufacturing any knowninsulated electric wire, for example, by melt extruding the insulatingresin. After the insulating layer is formed, the resin forming theinsulating layer may be crosslinked, for example, by irradiating it withionizing radiation in order to improve the heat resistance of theinsulating layer.

In twisting section 113, two insulated electric wires 13 supplied aretwisted together to form a core electric wire 14. This core electricwire 14 is transferred to tape member-winding section 115.

In tape member-winding section 115, core electric wire 14 transferredfrom twisting section 113 and tape member 15 supplied from tape membersupply reel 114 are merged, and tape member 15 is spirally wound aroundcore electric wire 14 on the outer circumference thereof to form atape-wound core electric wire 34. This tape-wound core electric wire 34is transferred to a first sheath layer-covering section 116. Here, animaging device 200 may be arranged between tape member-winding section115 and first sheath layer-covering section 116. Since tape member 15 istransparent to light having a predetermined wavelength, the state ofinsulated electric wire 13 in tape-wound core electric wire 34 can beobserved by imaging device 200.

First sheath layer-covering section 116 is connected to a storagesection 116 a in which a resin material such as a polyolefin-based resinis stored. In first sheath layer-covering section 116, the resinmaterial supplied from this storage section 116 a is extruded on theouter circumference of tape-wound core electric wire 34 and coverstape-wound core electric wire 34. In this way, first sheath layer 16 isformed so as to cover tape-wound core electric wire 34 on the outercircumference thereof. First sheath layer 16-covered, tape-wound coreelectric wire 35 is transferred to a second sheath layer-coveringsection 117.

Second sheath layer-covering section 117 is connected to a storagesection 117 a in which a resin material such as a polyurethane-basedresin is stored. In second sheath layer-covering section 117, the resinmaterial supplied from this storage section 117 a is extruded on theouter circumference of first sheath layer 16 formed by first sheathlayer-covering section 116 and covers first sheath layer 16. In thisway, second sheath layer 17 is formed so as to cover first sheath layer16 on the outer circumference thereof, to form an electrically insulatedcable 50 that is covered with a covering layer 18 of a bilayer structurecomprised of first sheath layer 16 and second sheath layer 17. Aftersecond sheath layer 17 is formed, electrically insulated cable 50 may beirradiated with electron beam or the like in order to crosslink a resinof covering layer 18 and thereby improve the scratch resistance. Thiselectrically insulated cable 50 is transferred to cooling section 118,in which covering layer 18 is cooled and cured, and thereaftertransferred to cable winding reel 119 for winding.

The above description includes the features additionally noted below.

(Additional Note 1)

An electrically insulated cable comprising:

a core electric wire;

a tape member covering the core electric wire; and

a covering layer covering the tape member;

wherein:

the core electric wire includes a plurality of insulated wires;

the insulated wires each include a conductor and an insulating layercovering the conductor; and

the tape member has a minimum value of transmittance of 70% or more in awavelength range of no less than 400 nm and no more than 800 nm.

(Additional Note 2)

The electrically insulated cable according to additional note 1, whereinthe tape member comprises at least one compound selected from the groupconsisting of cellulose, polyethylene terephthalate and polyethylene.

(Additional Note 3)

The electrically insulated cable according to additional note 1 or 2,wherein the tape member has a thickness of no less than 3 μm and no morethan 200 μm.

(Additional Note 4)

The electrically insulated cable according to any of additional notes 1to 3, wherein the covering layer includes a first sheath layer coveringthe tape member and a second sheath layer covering the first sheathlayer.

(Additional Note 5)

The electrically insulated cable according to any of additional notes 1to 4, wherein the plurality of insulated wires each have the samediameter, and the cross-sectional area of the conductor in each of theplurality of insulated wires is no less than 1.5 mm² and no more than 3mm².

EXAMPLE

Hereinafter, the present disclosure will be specifically described basedon the examples thereof, but the present invention will not be limitedto the following examples.

<<Manufacturing of Electrically Insulated Cable>>

<Preparation of Materials>

The following materials were prepared to produce an electricallyinsulated cable.

1) A material for forming an insulating layer: a flame-retardantpolyethylene-based resin (manufactured by RIKEN TECHNOS CORPORATION;trade name: ANQ9729T)2) A material for forming a first sheath layer: a non flame-retardantpolyethylene-based resin (manufactured by DuPont-Mitsui PolychemicalsCo. Ltd. (presently, DOW-MITSUI POLYCHEMICALS CO., LTD.); trade name:EVAFLEX EV360)3) A material for forming a second sheath layer: a non flame-retardantpolyurethane-based resin (manufactured by BASF; trade name: ElastollanET385)4) A material for forming a tape member

-   -   A cellophane: 20 μm in thickness (manufactured by Rengo Co.,        Ltd.)    -   A PET tape: 14 μm or 30 μm in thickness (manufactured by Toray        Industries, Inc.; trade name: Lumirror)    -   A PE tape: 50 μm in thickness (manufactured by Futamura Chemical        Co., Ltd.)    -   Tape A: a polyester paper 9 g/m² manufactured by Daio Paper        Corporation    -   Tape B: a rayon paper 11 g/m² manufactured by Daio Paper        Corporation    -   Tape C: a rayon paper 25 g/m² manufactured by Daio Paper        Corporation

<Measurement of Transmittance of Tape Member>

For each of the above-described tape members, a transmission spectrum ina wavelength range of no less than 400 nm and no more than 800 nm wasmeasured using UV-2450 manufactured by Shimadzu Corporation to determinethe minimum value of transmittance.

<Production of Electrically Insulated Cable>

An element wire, made of a copper alloy, having an outer diameter of0.08 mm was prepared. The fifty-two element wires were twisted togetherto produce a twisted wire. The seven twisted wires were twisted togetherto produce a conductor (twisted twisted wire). The outside diameter ofthe conductor was 2.0 mm. A flame-retardant polyethylene-based resin wasmelt extruded on the conductor on the outer circumference thereof toform an insulating layer having a thickness of 0.4 mm, so as to producean insulated electric wire.

The two insulated electric wires produced were twisted together toproduce a core electric wire. Each of the tape members shown in Table 1was spirally wound in one layer with a winding width of 3 mm around theproduced core electric wire on the outer circumference thereof to coverthe core electric wire on the outer circumference thereof with the tapemember. A non-flame retardant polyethylene-based resin was melt extrudedon the tape member-wound core electric wire on the outer circumferencethereof and cover it, so as to form a first sheath layer having athickness of 0.5 mm. Thereafter, a non-flame retardantpolyurethane-based resin was melt extruded on the first sheath layer onthe outer circumference thereof and cover it, so as to form a secondsheath layer having a thickness of 0.5 mm. Samples of the electricallyinsulated cables with Sample Numbers 1 to 7 were prepared by the aboveprocedure. Here, Sample Numbers 1 to 4 correspond to the examples.Sample Numbers 5 to 7 correspond to comparative examples.

<Visibility Test>

Each of Sample Numbers 1 to 7 was subjected to a visibility testaccording to the following procedure. That is, a wire assembly coveredwith a tape member was used and was confirmed whether or not the stateof an insulator included therein (such as the presence or absence of abump in an insulating layer, the presence or absence of a contaminant ordisordered twisting of the assembly) could be visually recognized byvisual observation. Each sample was evaluated as A when the internalinsulating state could be confirmed by visual observation, and as B whenit could not be confirmed by visual observation. The results are shownin Table 1.

TABLE 1 Sample Number 1 2 3 4 5 6 7 Tape Forming material Cellophane PETPET PE Tape A Tape B Tape C member Thickness (μm) 20 14 30 50 20 35 60Transmittance* 82 80 81 72 45 32 3 (%) Visibility A A A A B B B

The minimum values of the transmittance with respect to light having awavelength in the range of 400 to 800 nm are shown.

Tape A: a polyester paper 9 g/m² manufactured by Daio Paper CorporationTape B: a rayon paper 11 g/m² manufactured by Daio Paper CorporationTape C: a rayon paper 25 g/m² manufactured by Daio Paper Corporation

From the results shown in Table 1, it has been found that each of theelectrically insulated cables of Sample Numbers 1 to 4 was excellent invisibility, even if the core electric wire was covered with the tapemember, for the insulated electric wire included therein.

The embodiments and examples now disclosed are exemplary in allrespects, and should be considered not to be restrictive. The scope ofthe present invention is defined by the claims rather than theembodiments and examples described above, and is intended to include theequivalents to the claims and all modifications within the scope of theclaims.

REFERENCE SIGNS LIST

11, 21 a, 21 b: conductor; 12, 22 a, 22 b: insulating layer; 13, 23 a,23 b: insulated electric wire; 14, 24: core electric wire; 15, 25: tapemember; 16, 26: first sheath layer; 17, 27: second sheath layer; 18, 28:covering layer, 34: tape-wound core electric wire; 35: first sheathlayer-covered, tape-wound core electric wire; 50, 60: electricallyinsulated cable; 111; manufacturing apparatus; 112: insulated electricwire supply reel; 113: twisting section; 114: tape member supply reel;115: tape member-winding section; 116: first sheath layer-coveringsection; 117: second sheath layer-covering section; 116 a, 117 a:storage section; 118: cooling section; 119: electrically insulated cablewinding reel; 200: imaging device.

1. An electrically insulated cable comprising: a core electric wire; atape member covering the core electric wire; and a covering layercovering the tape member; wherein: the core electric wire includes aplurality of insulated electric wires; the insulated electric wires eachinclude a conductor and an insulating layer covering the conductor; andthe tape member has a minimum value of transmittance of 70% or more withrespect to light having a wavelength in the range of no less than 400 nmand no more than 800 nm.
 2. The electrically insulated cable accordingto claim 1, wherein the tape member comprises at least one compoundselected from the group consisting of cellulose, polyethyleneterephthalate and polyethylene.
 3. The electrically insulated cableaccording to claim 1, wherein the tape member has a thickness of no lessthan 3 μm and no more than 200 μm.
 4. The electrically insulated cableaccording to claim 1, wherein the covering layer includes a first sheathlayer covering the tape member and a second sheath layer covering thefirst sheath layer.
 5. The electrically insulated cable according toclaim 1, wherein the plurality of insulated electric wires each have thesame diameter, and the conductor in each of the plurality of insulatedelectric wires has a cross-sectional area of no less than 1.5 mm² and nomore than 3 mm².
 6. The electrically insulated cable according to claim1, which is an electrically insulated cable to be mounted on a vehicle.7. The electrically insulated cable according to claim 6, which is anelectrically insulated cable for an electric parking brake.
 8. Theelectrically insulated cable according to claim 6, which is anelectrically insulated cable for an antilock brake system.